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rcu: add rcu_read_lock_dont_migrate() 

migrate_disable() is called to disable migration in the kernel, and it is
often used together with rcu_read_lock().

However, with PREEMPT_RCU disabled, it's unnecessary, as rcu_read_lock()
will always disable preemption, which will also disable migration.

Introduce rcu_read_lock_dont_migrate() and rcu_read_unlock_migrate(),
which will do the migration enable and disable only when PREEMPT_RCU.

Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/r/20250821090609.42508-2-dongml2@chinatelecom.cn
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Menglong Dong 2025-08-21 17:06:03 +08:00 committed by Alexei Starovoitov
parent 4223bf833c
commit 1b93c03fb3
1 changed files with 14 additions and 0 deletions
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14
include/linux/rcupdate.h
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@ -962,6 +962,20 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
preempt_enable_notrace();
}
static __always_inline void rcu_read_lock_dont_migrate(void)
{
if (IS_ENABLED(CONFIG_PREEMPT_RCU))
migrate_disable();
rcu_read_lock();
}
static inline void rcu_read_unlock_migrate(void)
{
rcu_read_unlock();
if (IS_ENABLED(CONFIG_PREEMPT_RCU))
migrate_enable();
}
/**
* RCU_INIT_POINTER() - initialize an RCU protected pointer
* @p: The pointer to be initialized.